Radio aid to navigation



Feb. 5, 1952 Filed Dec. 3l 1947 @VfR/1m? V r u 1- A A64/wm x F ,3 13,/ 39 37 g5 .a5 37 g 31 31 31 Jfznar: David G.C.Luck y /7 7' TOR/VE Y Feb. 5, 1952 D. G. c. LUCK 2,584,599

RADIO AID TO NAVIGATION Filed Dec. 3l 1947 2 SHEETS-SHEET 2 31 az 31 llfwmf 51W?! a VWK? ATTORNEY Patented Feb. 5, 1952 2,584,599 RADIO AID To NAVIGATION David G. C. Luck, Princeton, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application December 31, 1947, Serial No. 794,937

3 Claims. (Cl. 178-6.8)

This invention relates to radio aids to navigation, and its principal object is to provide improvements in course-defining systems such as ranges and localizers.

Certain more or less comprehensive radio navigation systems have been devised involving television links between ground stations and the craft to be directed or guided; one of the more specific objects of the present invention is to provide a course-defining system which utilizes some of the equipment required for such television links.

Ordinarily, instrument landing systems or ground approach systems for aircraft require a beacon transmitter to be located in line with the runway. 'Ihis constitutes a hazard even though the beacon is placed well'beyond the end of the runway. Accordingly, it is a further ob'- ject of this invention to provide a radio localizer system in which the beacon is located off the line of the runway.

Still another object of this invention is to pro-A vide improved methods and means for visually indicating deviation of-a mobile craft from a prescribed path or course.

The invention will be described with reference to the accompanying drawings, wherein:

Figure 1 is a plan view of a portion of an airport, showing a landing strip or runway and a localizer system, Y

Figure 2 is a schematic block diagram of a localizer system embodying the present invention, ,v

Figure 3 is an oscillogram representing signals produced in one mode of operation of the system of Figure 2, Y

Figure 4 is a pictorial representation of a television display produced in response to the signals shown in Figure 3,` e

Figure 5 is an oscillogram representing signal produced in an alternative'mode of operation of the system of Figure 2, and

Figure 6 shows a television display of the type produced in response to signals like those of Figure 5.

Refer first to Figure 1, which shows the general arrangement of a localizer system according to this invention. Two transmitters I and 3 are located on opposite sides of the landing strip 5, in a line perpendicular to the landing strip and at equal distances therefrom.

`The transmitters I and 3 may operate on the same carrier frequency.` Each aircraft using the present system carries a, television receiver designed torespond to both transmitters I and 3. 55 causing the pulse generator I1 to makea pulse;

Referring to Figure 2, a television camera 'I, such as described in C. V. Bedford Patent 2,237,403, is coupled to the transmitter I through a mixer circuit 9. A synchronizing signal generator II, such as shown in C. V. Bedford Patent 2,258,943, provides line and frame synchronizing pulses which control the scanning circuitsV in the camera 'I and are applied, together with the video signal output of the camera, to the mixer 9. The mixer may be as shown in R. L. Campbell Patent 2,092,875. Visual information, such as a map, written instructions, weather information, and theV like, are displayed on a writing surface I3 disposed in front of the camera I.` A picture of this is sent by way of the transmitter I, which may be of the general types described in Hansell Patent 2,032,208 or Lindenblad Patent 2,052,888, to all aircraft in the vicinity and may be reproduced on an airborne television receiver I4. The

receiver is of conventional type as shown in Carlson Reissue Patent Re. 20,700. f

In :addition to the television signals from the camera 'I, the outputs of two pulse generators I5 and II are applied to the mixer 9. The pulse generators I5 and I1 may be blocking oscillators or other known devices, for example, as shown in said Bedford Patent 2,258,943 or as shown lin Bedford Patent 2,223,812, designed to have a freerunning frequency approximately equal -to the line repetition frequency. of the television system. Line synchronizing pulses fromthesync generator II are applied to the pulse generators I5 andv I 'I through delay circuits I9 andZI ,respectively, which may be of the type shown in Bedford Patent 2,145,332.

The transmitter 3, similar to the transmitter I, is modulated by a third pulse generator 23, similar to the generators I5 and I'I and controlled by line synchronizing pulses from the sync generator I I through a similar delay circuit 25. The output of the pulse generator 23 is periodically keyed on and off by aswitch 21, drivenfcontnuously by a motor 29.

The adjustment and operation of the described system may be substantially as follows: 'I'he .delay.. circuit 25 is adjusted to excite the pulse generator 23 and to provide a brief pulse substan` tially midway between each pair of linesynchronizing pulses.

causing the pulse generator I5 to produce a brief pulse shortly before each pulse from the generator 23. YThe delay circuit 2| provides some=:

what more delay than the delay circuit 25, thus The delay circuit .I9 provides somewhat less delay thanV the delay circuit 25,.

j, j, l j 2,584,599

3 slightly later than each pulse from the generator 23.

Figure 3 shows the time relationship between the various pulses; the line or horizontal synchronizing pulses 3l are superimposed on horizontal blanking pulses 33, as in a conventional television signal. The pulses are those provided bythe generator I5, and the pulses 31 represent the'output of thegenerator I1. These signals, and whatever picture signal is present, are transmitted by the transmitter I. the pulse generator 23 is shown in Figure- 3 ,as the pulse 39, and is transmitted by the 'trans-V mitter I at the center of the interval between the pulses 35 and 31. The pulse 3S is transmitted only when the switch 21 is closed. The amplitudes of the pulses 35, 31, 39 preferably, are equal to the maximum or black videorsignal amplitude, hence do notactuate the synchronizing signal circuits, while providing suitable contrast with picture elements It is assumed for the present that the television system isdesigned, as in conventional practice `in the United States of America, so that the minimum radio frequency signal level represents White in the picture, an intermediate signal level represents black, and sync pulses are at a level blacker than black. The signal shown in Figure 3 will produce a; display, on the screen of the receiver I, of the type shown in Figure 4. The pulses 35 make a black spot at the same point in each horizontal line, presenting the appearance of a vertical black stripe ill. The pulses 31- produce a similar verticalblack line 43. The pulses from the transmitter 3 produce the Vertical line IE5, which: is broken at intervals owing to periodic keyin'glby the switch 21. All of the vertical black lines are superimposed on the ,picture picked up by the camera 1; with the wave shown in Figure 3, the picture is simply a uniform gray as shown in Figure 4. Y

As long as the aircraft is on a course directly over the runway andY therefore equidistant from both transmitters I ,and 3, the line will appear midway between the lines 1H and 3 in the display provided bythe receiver I4. Now suppose the .craft gets oi course to the left; it will be closer to the transmitter I than it is to the transmitter. 3, and the pulses 39 will arriveearlier with respect to the pulses 35 and 3.1.. This will cause the dash line d5 of the television display to shift to the left, closer to the line 4I and further from the line 43. Similarly, ir" the craft is off course to the right, the line 115 shifts tothe right with respect to the lines lll and ii3. Thus the system :provides a clear, readily interpretable and continuous indication of the lateral positionv of the'aircraft with respectto the desired ight path. It will be apparent that the system will handle simultaneously any practical number of' aircraft, each displaying its own indication on its respective televisionreceiver independently o the positions of the others. Y

The output of f show only the central portion of the display of Figure 4, spreading it out to cover the screen. A modified type of display is shown in Figure 6, comprising a broad white stripe 41 down the center of the gray picture, with a narrower black line 49 nominally at the center of the white stripe. This can be produced by omitting the pulse generator I1 from the system of Figure 1 and designing the vgenerator I5 to provide a relatively wide pulse (corresponding to the width of the stripe 41) which is applied to the mixer 9 in such polarity as to modulate the transmitter I downward, i. e., in the direction of minimum radio frequency signal amplitude. The line 49 may be made solid as shown in Figure 6 by omitting the' switch 21. Figure 5 shows the envelope vof the radio frequency signals received at the receiver I4. The line synchronizing and blanking pulses 3| and 33 respectively are the same as in Figure 3. The gaps 5I represent the negative-going wide pulse from the generator I5, and the narrow pulses 39 are those transmitted by thetransmitter I. The lateral position of the black line d3 with respect to fthe stripe 41 indicates the lateral position of the aircraft `with respect to the desired night path.

It will be apparent that the display of Figure 6 may be reversed, presenting the appearance of a white line ona broad black stripe, by reversing the sense of the video modulation as mentioned above. Although the invention has been described as involving the use of a singleA carrier frequency for both transmittersl and 3,y as is preferred at present, it Will be understoodwithout further illustration that dierent frequenciesI may be used, with separate airborne television receivers controlling the display on a single cathode ray tube.

I claim as my invention: d Y

1. In a radio system for guiding mobile craft, a ground station including two spaced equi-directional transmitters;a television camera and synchronizing signal generator means connected to only one of said transmitters; means re sponsive to line synchronizing signals from .said synchronizing signal generator to produce a video signal representing a double-line reference pattern, and means applying ,said signal to said one of said transmitters together with the video output of said camera; means4 responsive to said line synchronizing signals to produce a further Videorsignal representing a mark which is distinguishable from said reference pattern,y

and means applying said further video signal to the other of said transmitters; common television receiver means on one of the craft to be guided, responsivetosaid ground station transmitters toproduce a 'composite visual display showing both said reference pattern and said mark, said markbeing positioned between said double lines of said pattern in said display in accordance' with the position of said, craft with respect to a predetermined course normal to a line connecting said transmitters.

' 2. In a radio system for guiding mobile craft, a ground station includingtwo spaced equi-directional transmitters; a television camera andy synchronizingsignal generator means connected to only one of` said transmitters; means re` sponsive toline synchronizing signals from said synchronizing signal generator to produce a` video signal representing a pair of vertical lines and means applyingsaid signalto one of said transmitters together with the video youtput of I said camera; means responsive to said. lineisyn chronizing signals to produce a further video signal representing a third vertical line which distinguishable from said first mentioned lines, and means applying said further video signal to the other of said transmitters; common television receiver means on one of the craft to be guided, responsive to both of said ground station transfn mitters to produce a visual display showing al1 of said vertical lines, said third line being positioned between said rst mentioned pair of lines in said display in accordance with the position of said craft with respect to a predetermined course normal to a line connecting said transmitters.

3. In a radio system for guiding mobile craft, a ground station including two spaced equi-directional transmitters; a television camera and synchronizing signal generator means connected to only one of said transmitters; means responsive to line synchronizing signals from said synchronizing signal generator to produce a video signal representing a pair of vertical lines, and means applying said signal to one of said transmitters together with the video output of said camera; means responsive to said line synchronizing signals to produce a further video signal representing a third vertical line which is distinguishable from said rst mentioned lines, and means applying said further video signals to the other of said transmitters; common television receiver means on one of the craft to be guided,

responsive to both of said ground station transmitters to produce a visual display showing all 5 of said vertical lines, said third line being positioned with respect to said rst mentioned pair of lines in said display in accordance wth the position of said craft with respect to a predetermined course normal to a line connecting said transmitters.

DAVID G. C. LUCK.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number l Name Date 2,070,651 Dowsett Feb. 16, 1937 2,150,551 Kemp Mar. 14, 1939 2,226,860 Grieg Dec. 31, 1940 2,267,715 Bowen Dec, 30, 19-'11 2,284,373 Kemp June 2, 1942 2,298,476 Goldsmith Oct. 13, 1942 2,307,029 Elm Jan. 5, 1943 2,399,671 Gage May 7, 1946 2,428,427 Loughren Oct. 7, 1947 2,428,966 Gage Oct. 14, 1947 2,480,068 Woli Aug. 23, 1949 2,481,410 Goldsmith Sept. 6, 1949 2,490,268 Herbst Dec. 6, 1949 OTHER REFERENCES Teleran Proposal, Electronics, vol. 19, No. 2, 

